Work has been carried out on a number of structural problems related to proteins derived from the HIV-1 virus. We determined the structure of a mutant protease that exists as a metastable monomer.We applied novel methodological approaches and devised NMR experiments to measure residual dipolar couplings.The Mutants of the potent HIV-inactivating molecule cyanovirin-N were structurally characterized and their binding to high mannose carbohydrates was investigated.